Output method and apparatus for estimating image quality prior to output

Abstract: An output apparatus and method is capable of transferring information showing a print data amount, determining a memory amount and estimating whether an inferior image will be output or not in accordance with the print data amount and memory amount. Accordingly, the apparatus and method can determine in advance whether to transfer the data, whether to print the data and whether to provide a display to an operator indicating that an output image will be of inferior quality.

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates to an output apparatus such as a printer and a method for transferring data that estimates whether image data will produce an inferior quality image or not prior to output. Related Background Art When image data is transferred from a host computer to a printer, the image data may be complicated and the printer may have insufficient memory to store all the image data. As a result, an image printed in response to the stored image data will be of inferior quality. Nevertheless, recently some printing devices have been developed which will automatically output the image data even if it results in an inferior image. If the operator at the printer is unaware of the problem, the resultant image may be inexplicable. The operator may try to output the image data again, resulting in wasted time, or may erroneously conclude that the printer is malfunctioning. US-A-5216754 describes a printing system preventing failures and interruptions associated with the inability of an image generation subsystem to generate a page in real time by determining the complexity of a page content prior to its submission to the subystem. The page may be automatically simplified. No information associated with the content of the page is transmitted in advance of the print data of the page. SUMMARY OF THE INVENTION The present invention has been made in consideration of the above situation, and has as one of its objects to provide an output apparatus and method capable of estimating image quality before printing. Another object of the present invention is to provide an output apparatus and method capable of estimating image quality before print data is transferred to a printer. Still another object of the present invention is to provide an output apparatus and method capable of estimating image quality and controlling further data processing in accordance with the estimation. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a printing apparatus in accordance with a first embodiment of the present invention. Fig. 2 is a flowchart showing processing steps of a method operative in the first embodiment. Fig. 3 is a flowchart showing processing steps of a method operative in a second embodiment. Fig. 4 is a flowchart showing processing steps of a method operative in a third embodiment. Fig. 5 is a perspective view of a laser beam printer. Fig. 6 is a perspective view of the main body of an ink-jet printer. Fig. 7 is a block diagram of a control unit of the ink-jet printer of Fig. 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a block diagram of a printing apparatus, in this example a laser beam printer operative in accordance with an embodiment of the present invention. Numeral 1 denotes a host computer which produces print data including, for example, at least character codes and control codes for editing or control of outputting the character codes, and transfers the print data to a printer control unit 101. In printer side 30, numeral 2 denotes an image inferiority estimating unit for determining whether data from the host computer 1 can be outputted without producing an inferior image. Numeral 3 denotes an input buffer for temporarily storing print data from the host computer 1. Numeral 4 denotes a data analyzing function unit for analyzing data stored in the input buffer 3. Numeral 5 denotes a buffer memory for storing print data which are analyzed by the data analyzing unit 4. Numeral 6 denotes an output process function unit for converting the data in the buffer memory 5 to dot patterns and for storing the patterns in an image memory 7. A control unit 20 is defined as including the data analyzing unit 4 and the output process unit 6. In this embodiment, the capacity of the image memory 7 is less than one page image of data, but is at least two lines, or two groups of lines, of image data. The two lines (or two groups of lines) are arranged such that when transferring image data of one line through interface 8 to a print engine 9, image data can be stored in the other line. The effective size of the image memory 7 depends on the total amount of memory in the apparatus. Therefore, for example, if a memory card is attached to the apparatus, the effective size of the image memory 7 can be increased up to one page. Numeral 10 denotes a ROM for storing control programs, such as a program described in connection with Figs. 2-4, and, for example, font data. Fig. 5 is a cross-sectional view of a recording apparatus, such a laser beam printer, to which the output method of the present invention is applicable. A main body 100 (printer) of the apparatus receives and stores print data (character information etc.) from information and macro instructions supplied from the external host computer 1, generates and forms character patterns and forms an image on a recording sheet constituting the recording medium. An operation panel 300 includes switches and LED indicators for various operations and a printer control unit 101 includes control elements other than those in the host computer 1 and the print engine 9 described in connection with Fig. 1 for controlling the entire printer 100 and analyzing the character information supplied from the host computer 1. The printer control unit 101 converts the character information into a video signal for the corresponding character patterns and supplies the video signal to a laser driver 102, which in turn drives a semiconductor laser 103 by switching a laser beam 104 emitted from the semiconductor laser 103 on and off according to the input video signal. The laser beam 104 is laterally deflected by a rotary polygon mirror 105 to scan an electrostatic drum 106, thereby forming an electrostatic latent image of the character patterns thereon. The latent image is developed into a visible image by a developing unit 107 positioned around the electrostatic drum 106 and transferred onto the recording sheet. The recording sheet is a cut sheet contained in a cassette 108 mounted on the main body 100 and supplied therefrom by a feed roller 109 and transport rollers 110 and 111 to the electrostatic drum 106. A change in density is achieved by controlling the rotation speed of the rotary polygon mirror 105, the rotation speed of the electrostatic drum 106 and the rate of transferring data to the laser driver 102 (the number synchronizing signal clocks for serially transferring bit data from the image memory 7). The operation of the printer control unit 101 will now be described in connection with the structure illustrated in Fig. 1. If an application program produces a print request in the host computer 1, the host computer 1 produces a print spool file containing the requested print data. When the file is complete, the host computer 1 reads data from the file and transfers it to the printer control unit 101 as print data. In this embodiment the host computer 1 determines each kind of data to be included while producing the file. The host computer 1 then transfers the result of the determination and information on the size of the file to the printer control unit 101, where the result and information are input to the image inferiority estimating unit 2. The image inferiority estimating unit 2 determines whether and to what degree the apparatus should reduce the density of the image data when printing an output image. The reason for reducing the density is to enable a page printer engine to execute a print process for each line. For example, while the print process for one line is being executed, the subsequent image data for the next line are produced and stored. However, if there is a very large amount of subsequent image data, it cannot be converted into dot data in time before the next print process. Therefore, by reducing the density, the amount of converted data and the necessary memory area can be reduced, and the apparatus can execute the conversion process in time. If the apparatus has enough memory, the line or group of lines can be large while still leaving enough time to convert the image data. In that case, there is rarely a need to reduce density. In practice, it is difficult to determine whether the data are complicated or not for each line unit. Therefore, in this embodiment, the apparatus determines whether the data are complicated or not for every page unit. The image inferiority estimating unit 2 compares the current memory amount in the apparatus and the data which are transferred from the host computer 1 and returns the result to the host computer 1. If the transferred result indicates a high possibility of image inferiority, that is, that there is insufficient memory to hold all the image data, the host computer 1 produces a display to this effect on the screen of the host computer 1. After that, if an operator still wishes to continue executing the printing process, he can actuate a manual switch to cause the apparatus to execute the printing process, whose result may be an inferior image. If-the transferred result shows a low possibility of image inferiority, the host computer 1 continues transferring data to the apparatus without interruption or display. Fig. 2 is a flowchart that shows processing steps in this embodiment. In step S1, the control unit 20 of the printer side 30 receives the information which shows the amount of print data to be transferred before it is transferred from the host computer 1. In step S2, the control unit 20 receives information on the kinds of data to be transferred, for example, image data, text data etc. In step S3, the control unit 20 determines a current memory amount of the apparatus and in step S4 the control unit 20 calculates or retrives an appropriate threshold level which will ensure sufficient image quality at each kind of data in accordance with the memory amount. In step S5, the control unit determines if the data fails to exceed the threshold level or not. If NO in step S5, the flow advances to an end step and the apparatus prepares for receiving the print data. If YES in step S5, the flow advances to step S6. In step S6, the apparatus transfers information indicating that a printout of the image will be inferior to the host computer 1. Fig. 3 is a flowchart that shows processing steps of an example not covered by the invention. One difference from the embodiment previously disclosed is that the host computer 1 determines whether image inferiority will result or not instead of the apparatus. In step S11 in Fig. 3, the host computer 1 determines what kinds of data to transfer, for example, such as image data, text data, figure data, before transferring print data. The flow advances to step S12, in which the host computer 1 determines an amount of print data. In step S13, the host computer 1 calculates the amount memory area necessary to normally execute the output (printing) process. In step S14, the host computer 1 determines a current memory amount of the printer from the printer. In step S15, the host computer 1 determines whether there is enough memory area for the print data or not. If YES in step S15, the process goes to step S17 in which the host computer 1 normally transfers data to the printer. If NO in step S15, the process goes to step S16 in which the host computer 1 controls the printer to delete data, for example, a temporary file or temporarily stored data, from the memory in the printer. After that, the flow returns to step S15 and step S17. In step 17, the host computer 1 transfers data to the printer. In this explanation, the host computer 1 may control the printer to transfer information showing the memory amount or the operator may previously set this information in a printer driver of the host computer 1. The control unit 20 has the function of deleting data in accordance with the instruction of the host computer 1. Fig. 4 is a flowchart which shows steps of a further example not covered ley the invention. In step S21, an operator instructs the host computer 1 whether an output process should continue or not if the image will be inferior in accordance with a print indication by an application program. In step S22, the host computer 1 determines whether there will be image inferiority or not. If YES in step S22, the flow advances to step S23. In step S23, the host computer checks the designated mode. If YES in step S23, i.e. if the designated mode is the printing mode to print even an inferior image, the flow advances to step S24. In step S24 the host computer 1 transfers print data to the printer. If NO in step 23, the flow advances to step S25. In step S25, the host computer 1 deletes the printer data, stops transferring print data to the printer, produces a display indicating that image inferiority will occur and stops printing. Therefore, the operator can understand what has happened and why the image was not printed. As described above, the host computer 1 can estimate the output image quality before printing. Therefore, it can alert the operator to avoid printing image data again after outputting inferior image data. Furthermore, in the embodiment of the invention previously disclosed, the information showing than an inferior image will be printed is transferred to the host computer 1. As an alternative, the necessary memory area can be calculated and displayed, or a list of temporary files can be displayed in turn. The display can alternatively or additionally be executed on a display of the printer, such as a liquid crystal display. Furthermore, a buzzer to inform the operator of inferior image quality can be provided. According to the present description, the input buffer memory 3, the buffer memory 5 and the image buffer memory 7 work independently and the print process uses a memory in line units, but this invention is not restricted to these features. For example, these memories can be designed as separate areas of one memory. If an area for the buffer memory 5 must enlarge so as to impringe on an area for the image buffer memory, the printer cannot output image data with high density. This invention is applicable to this case too. As described above, before transferring print data, this invention can determine whether image inferiority will occur or not. The apparatus of each embodiment described above utilizes a laser beam printer. However, the present invention is not limited to this and may be equally applied to other printers such as an ink-jet printer. Fig. 6 is a perspective view of the main body of an ink-jet recording apparatus IJRA to which the present invention can be applied. Referring to Fig. 6, a carriage HC engages with a helical groove 5005 of a lead screw 5004 rotated interlockingly with the normal/reverse rotation of a drive motor 5013 through driving force transmission gears 5011 and 5009 having pin (not shown), and can be reciprocated in directions indicated by arrows a and b . An ink-jet cartridge IJC is mounted on the carriage HC. A paper press plate 5002 presses the paper in the carriage movement direction through a platten 5000. Photosensors 5007 and 5008 are home position detecting means for detecting the presence of a lever 5006 of the carriage within this range to switch the rotational direction of the motor 5013. A member 5016 supports a cap 5002 for capping the front surface of a recording head. A suction device 5015 draws the ink from the cap to recover the recording head through an opening 5023 in the cap. A cleaning blade 5017 is moved back and forth by the member 5019, and the cleaning blade 5017 and the member 5019 are supported on a main body support plate 5018. The blade need not have this form, but can be replaced with a known cleaning blade. A lever 5021 starts suction to recover the recording head. The lever 5012 is moved together with movement of a cam 5020 engaged with the carriage. The driving force from the driving motor is controlled by a known transmitting means such as clutch switching. Capping, cleaning and suction recovery are performed by desired processes at the corresponding positions in accordance with the behavior of the lead screw 5004 when the carriage reaches the home position. If desired operations are performed at known timings, any scheme therefor can be employed. A control arrangement for executing recording control of the respective components in the primary apparatus will now be described with reference to the block diagram in Fig. 7. A control circuit includes an interface 1700 for inputting a recording signal, an MPU (microprocessing unit) 1701, a program ROM 1702 for storing control programs executed by the MPU 1701, a dynamic RAM 1703 for storing various types of data (e.g. the recording signal and recording data supplied to the head), a gate array 1704 for controlling supplying the recording data to a recording head 1708, a paperfeed motor 1709 for conveying a recording sheet, a head driver 1705 for driving the head, the motor drivers 1706 and 1707 for driving the paperfeed motor 1709 and the carriage motor 1710, respectively. The program ROM 1702 includes program as shown above, too. The operation of the above control arrangement is as follows. When a recording signal is input to the interface 1700, it is converted into print recording data by the gate array 1704 and the MPU 1701. The motor drivers 1706 and 1707 are driven to drive the recording head in accordance with the recording data supplied to the head driver 1705, thereby printing the recording information. As described above, the invention can provide an output apparatus and method capable of transferring information showing a print data amount, determining a memory amount and estimating whether an inferior image will be output or not in accordance with the print data amount and memory amount. Accordingly, the apparatus and method can determine in advance whether to transfer the data, whether to print the data and whether to provide a display to an operator indicating that an output image will be of inferior quality. An output apparatus and method is capable of transferring information showing a print data amount, determining a memory amount and estimating whether an inferior image will be output or not in accordance with the print data amount and memory amount. Accordingly, the apparatus and method can determine in advance whether to transfer the data, whether to print the data and whether to provide a display to an operator indicating that an output image will be of inferior quality.

Claims: An output apparatus connected to a host computer, the host computer providing print data to be transferred to said output apparatus and first information indicative of an amount of the print data to be transferred, where the print data to be transferred includes data corresponding to an image, said output apparatus comprising: receiving means for receiving from the host computer the first information indicative of the amount of print data to be transferred; determining means for determining second information indicative of an amount of memory space available to said output apparatus for storing the print data to be transferred; estimating means for estimating, in response to the first and second information, an estimated quality of an output image that said output apparatus can output in accordance with the print data to be transferred; and control means for controlling output of the image in accordance with the estimated quality. An output apparatus according to Claim 1, wherein said control means determines whether or not the estimated quality is at least as good as a threshold quality and controls output of the object image in response to the determination. An output apparatus according to Claim 2, wherein said control means inhibits output of the object image when the estimated image quality is less than the threshold quality. An output apparatus according to Claim 2, wherein said control means outputs a notification of inferior image quality to an operator when the estimated image quality is less than the threshold quality. An output apparatus according to Claim 4, further comprising manually actuable key means for entering a command to output the object image, wherein after said control means outputs the notification, said control means outputs the object image only in response to actuation of said key means. An output method for controlling an output apparatus connected to a host computer, the host computer providing print data to be transferred to the output apparatus and first information indicative of an amount of the print data to be transferred, where the print data to be transferred includes data corresponding to an image, said output method comprising the steps of: receiving from the host computer the first information indicative of the amount of print data to be transferred; determining second information indicative of an amount of memory space available to the output apparatus for storing the print data to be transferred; estimating, in response to the first and second information, an estimated quality of an output image that the output apparatus can output in accordance with the print data to be transferred; and controlling output of the image in accordance with the estimated quality. An output method according to Claim 6, wherein said control step determines whether or not the estimated quality is at least as good as a threshold quality and controls output of the object image in response to the determination. An output method according to Claim 7, wherein said control step inhibits output of the object image when the estimated image quality is less than the threshold quality. An output method according to Claim 7, wherein said control step outputs a notification of inferior image quality to an operator when the estimated image quality is less than the threshold quality. An output method according to Claim 9, further comprising a step of manually actuating key means for entering a command to output the object image, wherein after said control step outputs the notification, said control step outputs the object image only in response to said actuation step.

Inventors: NAKAO MAKIKO, NAKAO, MAKIKO, NAKAO, MAKIKO, C/O CANON KABUSHIKA KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1994
Main classification: G06F3
IPC codes: G06K15, G06F3, B41J5